Jake is correct in point out that the GCWR is what is important for towing. It indicates how much weight your truck's engine, drivetrain, and frame can safely handle. The GVWR is simply a number calculated from the condition of the truck when it left the factory. The true capacity can be increased or decreased with modifications to the truck.
Want to decrease it, well then put on larger tires or lift the truck or lower it. Want to increase the load capacity then add overload springs and higher capacity tires. With some older trucks the addition of an axle truss was commonplace.
The truck manufacturers are not testing their trucks, nor the car magazines, based on real world conditions. The only exceptions were the recent 1-ton tests by mrtrailer.com and Car and Driver where actual trailer loads were use during the tests for acceleration, stopping distance, fuel economy, handling. I would not tow a 10,000 lb. trailer with a 1/2 ton truck or a 3/4 ton SUV as they are not up to the task regardless of the manufacturer's specs. If you have a problem with the trailer's brakes how many miles will it take to bring the rig to a complete stop?
Originally Posted by elkhornsun
Thanks @elkhornsun , but one can not simply add air bags upgrade axle and brakes and then figure the GVWR can increase by X lbs. The GVWR must never be exceeded, nor the Gross Axle Weight ratings no mater what extras you add. Any extras you add actually add weight to the vehicle. So if you add 100# of options this takes away 100# of available payload, true as you stated.
Not sure if you can alter axles and brakes and have the truck re-evaluated for an increased GVWR and have the sticker changed. I was going to look into this with the 2009 1500 I had, but the 2011 2500HD deal was to good and I upgraded. The local DOT (MOT here in Ontario) have had check points where they targeted those pulling trailers and a friend at work was pulled over. They placed his truck/trailer on the scale and looked at the sticker. and since he was under the GVWR off he went.
For towing, you need the Gross Combine Vehicle Rating (GCVR), which includes the truck and trailer. Or you need to know the max trailer weight rating for the truck. As noted, there are several other factors that determine the actual towing capacity of the truck, but the GCVR should never be exceeded, regardless (e.g. if the truck is rated for 10k, and you have a 20k hitch; its still only rated for 10k). Your equipment is the second factor after GCVR.
The Gross Vehicle Weight Rating (GVWR) is for the truck alone, and is a moot point once the trailer is connected. Unfortunately, you can't even believe the registration for a vehicle in certain states as it was very common to buy a truck and "increase" the GVWR during the title swap...the state didn't care as it typically meant a higher registration fee.
Bottom line is the door sticker is what they look at for GVWR...regardless of registration. That is as long as your under your registered GVWR, since then you are "breaking" the law if your over your registered weight; even if your actual weight is under your door sticker (money maker for them, not safety).
And unless the door sticker has GCVR posted, the DOT man will simply look at your axle ratings, and the truck GVWR, trailer GVWR, and truck/trailer tire load ratings...if you are under all of those they will likely send you down the road.